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Four isoforms of the signal-transduction and RNA-binding protein QKI expressed during chicken spermatogenesis
J Mezquita1, M Pau, C Mezquita
1Molecular Genetics Research Group, Faculty of Medicine, University of Barcelona, Spain. mezquita@medicina.ub.es
Abstract:
Genes expressed during spermatogenesis undergo alternative initiation and alternative splicing and may be under the control of a coordinated mechanism of RNA processing. A family of proteins that combine features of signal-transduction and RNA-binding molecules could be instrumental in this process. We have characterized a cDNA from adult chicken testis that codifies a highly conserved member of the STAR protein family, the orthologue of the mouse quaking gene qki. The predicted chicken protein differs only in four amino acids from the corresponding mouse protein. Messages of 7, 6, and 5 kb are expressed differentially during chicken spermatogenesis. The 5-kb message, the predominant form in adult testis, presents heterogeneity in the coding region, showing insertions of 51 and 75 bp and a deletion of 24 bp, which gives rise to four possible isoforms of the protein.
Insights
Chicken testis STAR proteins, orthologues of mouse quaking (qki), show differential expression and alternative splicing during spermatogenesis. This suggests a coordinated RNA processing mechanism controlling gene expression in male germ cells.
Area of Science:
- Molecular Biology
- Genetics
- Developmental Biology
Background:
- Spermatogenesis involves complex gene regulation, including alternative splicing and initiation.
- STAR proteins, with signal-transduction and RNA-binding domains, are implicated in RNA processing.
- The mouse quaking (qki) gene is crucial for spermatogenesis.
Purpose of the Study:
- To characterize a chicken STAR protein family member, the orthologue of mouse qki.
- To investigate the expression patterns and alternative splicing of this gene during chicken spermatogenesis.
Main Methods:
- cDNA characterization from adult chicken testis.
- Sequence analysis to compare chicken and mouse proteins.
- Northern blot analysis to examine mRNA expression during spermatogenesis.
Main Results:
- A highly conserved chicken STAR protein, orthologous to mouse qki, was identified.
- Chicken qki protein differs from mouse qki by only four amino acids.
- Three mRNA messages (7, 6, and 5 kb) were differentially expressed during spermatogenesis.
- The predominant 5-kb message exhibited coding region heterogeneity with insertions and deletions, leading to four potential protein isoforms.
Conclusions:
- Chicken STAR proteins, similar to mouse qki, are involved in spermatogenesis.
- Alternative splicing of the chicken qki gene generates multiple protein isoforms.
- These findings suggest a coordinated RNA processing mechanism controlling gene expression in chicken spermatogenesis.